Optical switch

ABSTRACT

The invention generally relates to an optical switch which in particular, is able to present a high-resolution color display. The aim of the invention is to produce an optical switch which has a simpler design than known constructive solutions and has a high degree of luminous efficiency and low parallax. The optical switch should also be guaranteed to function at approx. 550° C. The inventive e.g., LCD-type optical switch is characterized in that at least one of the support plates consists of color-structured dichroic polarization glass which is impressed with dichroic color filters, in that the dichroic color filters are situated within an orthogonal matrix in color filter layers and in that the color filter layers of the support plate, starting form the surface of the support plate, extend into the same to a depth of a few μm. Once the glass support plates have been structured, the color patterns remain stable to approx. 550° C. As a result of using the color-structured dichroic polarization filter, the invention requires at least one less polarization filter than conventional LCD&#39;s and therefore has a simpler construction.

In general terms, the invention concerns an optical switch, which inparticular can represent a high-resolution colour display. With itscolour and polarisation effects, the optical switch is not limited tothe visible spectral range. There is also the possibility oflight-intensity control in the UV and IR ranges as well as combinationswith applications in the visible spectral range.

Liquid crystal displays (LCDs) have long since been state of the art.They are distinguished by a low power demand and robust construction.For articles of daily use liquid crystal displays are used in a big way,being based on the principle that a twisted layer of liquid crystalrotates the polarisation level of light at different strengths accordingto whether an electrical field is fed or not. The light can then passthrough a second polarisation filter in one case and not in the other.

Such a component consists of two glass plates, the support plates,between which the liquid crystal substance is situated. Both glassplates support conductive, transparent electrodes and orientation layerson the inside. When no electrical field is active, the liquid crystalmolecules are oriented parallel to the glass plates. On the inside bothglass plates support microfine arrangements, which are twisted towardseach other (usually by 90° or 270°). Because the liquid crystalmolecules align themselves to the arrangements of the orientation layer,a twisting of the molecules towards each other takes place in the liquidcrystal layer. If an electrical current is fed between opposingelectrodes, this causes an alignment of the molecules in the fielddirection; the polarisation direction of a penetrating beam of light isno longer rotated.

The structure of a liquid crystal display usually includes twopolarisation filters in addition to other components. Each of thesefilters is aligned on the external surfaces of the support plates, andadditional colour filters for colour LCDs. Made up of many layers,conventional LCDs have a very complicated structure. The colour filtersare sensitive to high temperatures as they frequently consist of organicpolymer material. The light yields in conventional colour LCDs arerelatively small in general.

In accordance with DE 42 01 281 A1, a proposal is being made for theformation of substrate plates for liquid crystal displays suited to thecolour reproduction of images. This publication sets out the fact thatIt is usual with substrate plates for liquid crystal displays, thecontrol of which is carried out by means of a dot-matrix electrodestructure and which allow colour images, to form the colour pixels ofthe various primary colours directly onto a support plate. However, asthe colour pixels do not form any plain surface contours, they arefitted with a covering layer. The aim is to achieve a furtherdevelopment in this direction in accordance with DE 42 01 281 A1,whereby the colour filter layer formed from colour pixels is coveredwith an ultra-thin film or layer of glass. This measure is considerednecessary if substrate plates are used in displays, which have angles oftwist between the liquid crystal molecules of □ 90° or which only permita small distance between the cell plates. As a result of the plainsurface, now achieved with the aid of the covering, the aim is to bringabout a uniform switching behaviour of the liquid crystal molecules.This example of the state of the art shows what efforts are necessary toproduce high-calibre colour displays.

According to WO 94/20879, there is proposed a liquid crystal display,constructed with two support plates made of glass. A liquid crystalsubstance is located between the support plates. The support plates areprovided with transparent electrodes, and polarizers are placed on theouter sides of the support carriers.

Color-structured dichroic filters are arranged on at least one of thesupport plates, which filters lie within a matrix in the sense of colorfilter layers and are supported by the support plate or support plates.

Now reference is made to a DE patent application with the referencenumber 196 42 116.0-33: This patent application, with the title “Processfor structured energy transmission with electron beams”, concerns aprocess by which energy is transmitted with the electron beam for ashort time into limited surface elements onto preferably plain surfacesof objects—such as plates or tapes made of metallic, semi-conductive ordielectric materials or a combination of them. The useable machiningeffects are determined by the physical or chemical reaction of thematerials to the energy transmission with the electron beam. Thepreferred area of application is the structuring of surfaces onstrip-shaped objects of any length with a limited number of recurringstructural elements aligned like a matrix in columns and rows. Theessential inventive characteristic of the aforementioned patentapplication consists in the fact that the object to be machined is movedduring the energy transmission contactlessly under a mask, in such a waythat an electron beam is guided in the object's direction of movementoscillating at high frequency approximately vertical to the object'sdirection of movement over the recesses in the mask at a very high speedin relation to the object's movement.

One advantageous area of application is the highly productive structuredmachining of objects with relatively large surface areas. In the area ofthermal electron beam machining the process can be used among otherthings for the colour structuring of suitably sensitised glass surfaces.For example, in this way a substrate made from glass with a speciallyprepared thin surface layer can be fitted by electron beam machiningwith a colour pattern in a repeated structure, as is common in LCDtechnology for instance. In order to achieve the desired optical effect,four pixels, aligned in an orthogonal matrix in each case, are to besubjected to varying energy densities. During machining a thermal effectcauses the thin, prepared surface layer in the areas of the pixels torun through simultaneous temperature cycles, but with different maximumtemperatures, in order to obtain certain optical properties pixel bypixel.

With the process in accordance with patent application 196 42 116.0-33,the limits of known processes for energy transmission with electronbeams for machining materials have been overcome for the first time. Itis now possible to subject structural elements as well as the smallestsurface areas, e.g. pixels, to the electron beam defined in a particularalignment on the surface, in order to achieve certain machining effectsin this area.

It is the task of the invention to propose an optical switch, which incomparison with known construction solutions has a simplified structure,in which a high light yield and a low parallax is given. The aim is thatthe optical switch should have a relatively low sensitivity to theeffects of temperature as a direct consequence of the solution accordingto the invention. As has already been stated, the “Process forstructured energy transmission with electron beams”, in accordance withpatent application DE 196 42 116.0-33, is currently the latest state ofthe art. Another task of the patent application submitted here is to usespecial components, structured according to the process in accordancewith DE 196 42 116.0-33, corresponding to the patent applicationsubmitted here.

In accordance with the invention, the task is solved as set out in thefollowing, whereby reference is made to patent application 1 regardingthe fundamental inventive idea. The other advantageous features resultfrom patent applications 2 to 6.

Further observations are necessary on the solution according to theinvention. The support plates of the optical switch, which in particularrepresents a high-resolution display, consist of glass, into whichdichroic colour filters are impressed. These are support plates whichwere structured according to the process in accordance with DE 196 42116.0-23. The support plates can have a design that is either plain ornot plain. For the structure of the optical switch only one or allsupport plates, as will be set out, can consist of glass, into whichdichroic colour filters are impressed.

The dichroic colour filter layers of the support plates are generallyaligned one-sided on the support plates. In the case of specialapplications the dichroic colour filter layers are to be aligneddouble-sided on the support plates.

With double-sided dichroic colour filter layers similar or differentabsorption and polarisation effects can be achieved.

Each of the dichroic colour filter layers in the support plates can bemonochrome (monochrome display) or colour structured (polychromedisplay).

The dichroic colour filter layers are situated inside the glass matrixof the support plates, and they have a matrix-like distribution inaccordance with the manufacturing process. The colour patterns in thesecases have recurring structures and allow the structure of a displaycapable of full colour.

The dichroic colour filter layers of the support plates range from theglass surface into a depth of a few μm. To give an indication, depths ofmax. 10 μm here can be stated. The thickness of the colour zone can herealso be only a few tenths of a μm.

The dichroic colour filters have colour and polarisation effects in thevisible and/or invisible spectral range (UV, IR range).

To achieve low parallaxes, the structured colour filter layers of thesupport plates in an advantageous design are aligned on the side whichis in contact with the liquid crystal substance, i.e. to achieve thesmallest possible distance of the structured surfaces, these surfacesare situated on the inside. In principle, known alignments are beingused here, whereby, unlike the known state of the art, the structuredsupport plates in accordance with the process according to DE 196 42116.0-33 are used.

If the lowest possible parallax is not deemed important, one or both ofthe colour filters can be situated on the external sides of the supportplates, as is the case in principle with the known arrangements andfilter structures.

It is essential to emphasise that the colour patterns according to thestructuring of the support plates, insofar as they consist of glass,remain stable up to approx. 550° C./600° C. Other materials should by nomeans be ruled out here.

As will be explained, transmissive, reflective and transflectivestructures are possible.

The optical switches (e.g. of the LCD type), to be realised by usingdichroically structured support plates, are distinguished by asimplified structure, where in many instances at least one polarisationfilter is no longer necessary. The colour filters, dichroicallystructured, are situated in a layer, obviating the need for additionalwork with regard to compensating the level of the pixels. The filtersare distinguished by a high light yield, as the dichroic filters have alower basic absorption compared to conventional colour filters.

Some design examples shall explain the invention further.

The figures depict:

FIG. 1—transmissive colour LCD with the colour combination (red, yellow,blue; black)

FIG. 2—transmissive colour LCD with the colour combination (red, yellow,blue; white)

FIG. 3—reflective colour LCD with the colour combination (red, yellow,blue; white)

FIG. 4—transmissive colour LCD with the colour combination (red, yellow,blue)

FIG. 5—transmissive colour LCD with the colour combination (red, green,blue; white)

FIG. 6—optical switch for UV-A light (transmissive, extinction in narrowranges)

FIG. 7—optical switch for narrow-band UV-A light (transmissive)

FIG. 8—optical switch for broad-band UV-A light (transmissive)

THE REFERENCE MARKS USED DENOTE:

1—colour-structured dichroic glass

2—transparent segment electrodes

3—orientation level

4—transparent main electrode

5—glass support

6—front polariser

7—polarisation filter

8—incident light

9—outcoming light —to the observer

10—liquid crystal molecules

11—reflector

12—colour-structured dichroic glass

13—dichroic UV front polarisation glass

14—dichroic UV glass

15—dichroic colour-structured UV glass

16—dichroic colour-structured UV glass

dR—dichroic red

dG—dichroic yellow

dB—dichroic blue

R—red

G—yellow

B—blue

W—white

UV Pol 1—UV polarisation glass

UV Pol 2—UV polarisation glass

UV Pol 3—UV polarisation glass

λ1, λ2, λ3—outcoming UV-A light of varying wavelength

The transmissive colour LCD with the colour combination according toFIG. 1 consists of a colour-structured dichroic glass 1. The opticallyactive layer is one-sided and aligned on the inside. This layer wasmanufactured, according to the process stated before in the description,for structured energy transmission with electron beams, with the glasshaving dichroic red dR, dichroic yellow dG, dichroic blue dB. On thecolour-structured dichroic glass 1 there are transparent segmentelectrodes 2 and the first orientation layer 3 on the inside. On asecond glass support (with the reference mark 5) a transparent mainelectrode 4 and also a second orientation layer 3 (rotated 90° to thefirst) are aligned inside. Beneath the glass support 5 there is (on theoutside) a polarisation filter 7, and above the colour-structureddichroic polarisation glass 1 (also outside) a front polariser 6 islocated. Both polarisation filters are aligned twisted 90° to eachother.

The incident unpolarised light 8 comes through the front polariser 6,being polarised in a linear manner. It comes through thecolour-structured dichroic glass 1, where absorption in narrowwavelength ranges takes place, then through the liquid crystal layer, inwhich it is rotated by 90° in its polarisation direction when thecurrent is not fed (i.e. In a non-triggered state), through glasssupport 5 with polarisation filter 7. As a result of the orientation ofthe polarisation filter 7 there is no absorption. From the polarisationfilter 7 comes light 9, polarised in a linear manner, with thecomponents red, yellow, blue.

In the triggered state an alignment of the liquid crystal molecules inthe field direction takes place, the polarisation direction of the lightis no longer rotated. The light is fully absorbed in the polarisationfilter 7 (in all wavelength ranges of the visible spectrum), thetriggered segments appear black.

According to FIG. 2 the incident light 8 (unpolarised) directlypenetrates the colour-structured dichroic glass 1. One component of theelectrical field vector remains virtually unaffected, while in thesecond, rotated by 90°, absorption in narrow wavelength ranges takesplace. After leaving the colour-structured dichroic glass 1, white light(in a polarisation plane) is obtained with the colour components red,yellow, blue (in the polarisation plane rotated by 90° to the first).There is no front polariser.

In the non-triggered state the polarisation direction is rotated by 90°.After passing through the polarisation filter 7 (that is oriented insuch a way that it completely absorbs the white component, and letsthrough the coloured component rotated by 90° virtually unweakened),this light only has the colour components red, yellow, blue and ispolarised in a linear manner.

In the triggered state there is no rotation of the polarisationdirection of the light, so that the colour component is absorbed by thepolarisation filter 7, and the white component rotated by 90° can passthrough. The outcoming light is white and polarised in a linear manner(see reference mark 9 in FIG. 2).

FIG. 3 shows the structure of a reflective colour LCD with colourcombination, with a reflector 11 fitted outside on the polarisationfilter 7 (rear polariser). As far as absorption and colour combinationare concerned, the same effects occur, as shown in FIG. 2. It is merelythe reflector 11, as an additional component, that causes the reflectionof the light when it comes out of the polarisation filter 7.

The optically active layers are one-sided and aligned internally in FIG.2 and FIG. 3, as well as in FIG. 1.

In comparison to FIGS. 1, 2 and 3, FIG. 4 has a change.Colour-structured dichroic glasses (1), (12) are aligned here on bothsides of the liquid crystal layer (optically active layers on theinside, i.e. on the side in contact with the liquid crystal substance).In the triggered state, polarised white light comes in a partiallylinear manner from the glass with colour components in the polarisationdirection rotated by 90°. This out-coming light (see reference mark9—outcoming light) is perceived by the observer as slightly coloured. Inthe non-triggered state, the outcoming light is fully coloured andunpolarised.

In FIG. 5 the colour-structured dichroic glass 1, in contrast to FIG. 4,has the colour sequence red, blue 1, blue 2, while the colour-structuredglass 12 has the colour sequence red, yellow, blue. Through theoverlapping of blue and yellow in the path of the beam, green isproduced. With the use of a polarisation filter 7 (rear polariser), itis possible to switch between the states of colour (red, green, blue)and white.

In FIG. 6 an optical switch for UV-A light (transmissive) isrepresented.

The incident light 8 (UV-A light, unpolarised) passes through thecolour-structured, dichroic UV glass 15 (with the optically active layerone-sided and on the inside), further through the liquid crystal layerand finally through a colour-structured dichroic UV glass 16. Bothglasses (according to reference marks 15, 16) have an optically activelayer that is one-sided and on the inside. In the triggered state thereis a maximum of 50% extinction. In the non-triggered state, extinctionis almost total in the UV wavelength ranges indicated.

FIG. 7 shows an optical switch for narrow-band UV-A light, which isunpolarised. The incident light 8 passes through the dichroic UV glass13 (narrow band), with an optically active layer being one-sided and onthe inside.

The dichroic UV glass 14 has an optically active layer, which is alignedone-sided and on the inside. In the non-triggered state there is totalextinction, while in the triggered state UV-A light 9 comes out, whichis polarised in a linear manner. Transmission of the light in thetriggered state is approx. 50%.

In FIG. 8 an optical switch for broad-band UV-A light is represented,which deviates in its structure in comparison with FIG. 6 in that thedichroic UV glass 13 has optically active layers on both sides, but withspectrally different absorption maximums (broadband enlargement). Thedichroic UV glass 14 also has optically active layers on both sides withspectrally different absorption maximums. As in FIG. 6, extinctionoccurs place in the non-triggered state, while in the triggered statethe incident UV-A light is polarised in a linear manner, with thetransmission being approx. 50%.

What is claimed is:
 1. Optical switch, consisting of two support platesmade of glass, between which a liquid crystal substance is situated,said support plates being equipped with transparent electrodes, and atleast one of the support plates consists of colour-structured dichroicglass, into which these dichroic filters are impressed, with saiddichroic filters in form of colour and polarisation filter layers beingsituated inside a glass matrix, and the dichroic filters ranging fromthe support plate surface to a depth of about 10 μm.
 2. Optical switchaccording to claim no. 1, characterised in that the support platesconsist of plate glass.
 3. Optical switch according to claim no. 1,characterised in that at least one support plate has dichroic filtersimpressed on both sides.
 4. Optical switch according to claim no. 1,characterised in that in at least one support of colour-structureddichroic glass a monochrome filter layer is impressed.
 5. Optical switchaccording to claim no. 1, characterised in that the filter layer of atleast one support plate is arranged in such a way that it is in contactwith the liquid crystal substance.
 6. Optical switch according to claimno. 1, characterised in that the optical switch itself, as far as itsnumber of polarisation filters is concerned, consists of not more thanone polarisation filter.